Liquid crystal display

ABSTRACT

A liquid crystal display device, by which a reduction of costs of a color filter is realized and declining of the transmittance or reflectance due to an alignment error is suppressed, comprising a pair of substrates arranged facing to each other over a liquid crystal layer, wherein one substrate is formed pixels PXL arranged in matrix. Each pixel is formed a reflection portion for reflecting an outside light and a transmission portion for transmitting a light. The other substrate is formed a color filter colored to be different colors (red, green and blue) corresponding to respective pixels. One or more color adjusting windows CFW having a coloring concentration of zero or less than that of other portions are provided on reflection regions CFR superposing with reflection portions inside pixel regions corresponding to respective pixels.

TECHNICAL FIELD

[0001] The present invention relates to an active matrix type liquidcrystal display device, particularly relates to a so-called hybrid typeliquid crystal display device wherein both of a reflection portion and atransmission portion exist in each pixel, furthermore specificallyrelates to a configuration of a color filter able to be applied to bothof the reflection portion and the transmission portion.

BACKGOUND ART

[0002] A hybrid type liquid crystal display device is disclosed, forexample, in the Japanese Unexamined Patent Publication No. 11-52366 andthe Japanese Unexamined Patent Publication No. 11-183892. A hybrid typeliquid crystal display device performs reflection type display by usingan outside light by reflecting the outside light irradiating from thefront surface side on a reflection layer on the back surface side when asufficiently bright outside light (natural light and room lighting,etc.) can be obtained, while when sufficient outside light cannot beobtained, it performs transmission type display by using a light of abacklight arranged on the back surface side of the liquid crystaldisplay device.

[0003]FIGS. 1A and 1B are schematic views of an example of aconventional hybrid type liquid crystal display device. FIG. 1A showsthe configuration of a section of one pixel.

[0004] As shown in the figures, the hybrid type liquid crystal displaydevice comprises a pair of a first substrate 1 and a second substrate 2arranged facing to each other at the front and back. On the innersurface side of the first substrate 1 is formed a transparent commonelectrode 3, and on the inner surface side of the second substrate 2 isformed a pixel electrode 4. A pixel is formed at a part where the commonelectrode 3 formed on the first substrate 1 and respective pixelelectrodes 4 formed on the second substrate 2 face to each other. Bybeing matched with the pixel, a color filter CF is provided on the first(front side) substrate 1.

[0005] Below, the first substrate 1 provided with the color filter CFwill be referred to as a CF substrate in some cases in the presentspecification.

[0006] A liquid crystal layer 5 as an electric optical layer is heldbetween the pair of the first and second substrates 1 and 2 at the frontand back. The liquid crystal layer 5 blocks/transmits an incident lightfor each pixel in response to a voltage applied between the electrodes 3and 4.

[0007] The second (back side) substrate 2 is provided with a reflectionlayer 6. The reflection layer 6 has an opening for every pixel andflatly divides each pixel to a transmission portion T in the opening anda reflection portion R outside the opening. In the present example, thereflection layer 6 is made of a metal film formed on a relief shapesurface of the substrate 2 and composes a part of the pixel electrode 4explained above. Also, the transmission portion T is formed atransparent conductive film, such as ITO, and the opening explainedabove is formed and composes a part of the pixel electrode 4.

[0008] As is clear from the above explanation, the pixel electrode 4formed on the second substrate 2 has the hybrid configuration of themetal film provided to the reflection portion R and the transparentconductive film provided on the transmission portion T. Such a pixelelectrode 4 is driven for every pixel by a switching element, forexample, driven by a thin film transistor (TFT).

[0009] The second substrate 2 being formed the TFT for driving pixelswill be referred to as a TFT substrate in some cases in the presentspecification below.

[0010] The color filter CF is separately configured for a reflectionregion CFR corresponding to the reflection region R and a transmissionregion CFT corresponding to the transmission region T by using differentmaterials. As shown in the figure, a light transmits the color filter CFtwice in the reflection region CFR. On the other hand, a light transmitsthe color filter CF only once in the transmission region CFT.

[0011] Therefore, in order not to cause much difference in color tonebetween the reflection portion R and the transmission portion T, acoloring concentration of the reflection region CFR is made lower thanthat of the transmission region CFT in advance. For this reason, even apart of a color filter CF colored to be an identical color in anidentical pixel was conventionally produced by separate processes byusing different materials in the reflection region CFR and thetransmission region CFT.

[0012]FIG. 1B schematically illustrates a plane shape of a liquidcrystal display device shown in FIG. 1A. As shown in the figure,respective pixels PXL are separated in lattice by a black mask BM. Eachpixel PXL is flatly divided to a transmission portion T at the centerand a reflection portion R around it and has a so-called hybridconfiguration. The color filter is patterned so as to approximatelycorrespond to the pixels marked off by the black mask BM. Typically,pixel regions of the color filter corresponding to respective pixels PXLare colored to be three primary colors, red, green and blue.

[0013] A hybrid type liquid crystal display device aims to alwaysrealize an easy-to-watch display under any circumstances. Thus, itbecomes a reflection type display for displaying a screen by using areflection light in the same way as a printed matter in a brightcircumstance, while in a dark circumstance, it becomes a transmissiontype display by using a backlight. To realize a color display by such ahybrid type display, it is necessary to form a color filter adjusted tothe transmission type and a color filter adjusted to the reflection typeon the CF substrate side. Conventionally, a method of forming a colorfilter separately through a production process of a transmission type CFand a production process of a reflection type CF was general.

[0014] However, this method requires a longer production process andmore materials and kinds to be used. Therefore, there is a disadvantagethat a color filter used in a hybrid type display becomes double inproduction costs comparing with a color filter used in a normaltransmission type display.

[0015] Also, when forming both of the transmission type color filter andthe reflection type color filter in one pixel, there is a disadvantagethat the transmittance or reflectance declines when an alignment errorarises between the two.

DISCLOSURE OF THE INVENTION

[0016] An object of the present invention is to reduce costs of a colorfilter by realizing a reduced process with less materials and to providea liquid crystal display device comprising a color filter by whichdeclining of the transmittance or reflectance due to an alignment erroris not caused.

[0017] To attain the above object, a first aspect of the presentinvention is a liquid crystal display device characterized by comprisinga pair of first substrate and a second substrate arranged facing to eachother over a liquid crystal layer, the first substrate is formed pixelsarranged in matrix, and each pixel is formed a reflection portion toreflect an outside light and a transmission portion to transmit a light,and the second substrate is formed a color filter colored to bedifferent colors corresponding to respective pixels; wherein the devicecomprises one or more color adjusting windows having a coloringconcentration of zero or less than that of other portions are providedinside pixel regions corresponding to respective pixels and onreflection regions superposing with the reflection portions in the colorfilter.

[0018] Preferably, the color adjusting window is formed inside thereflection region leaving a distance of 2 μm or more from an edge of thereflection region. Also, the color filter comprises a plurality of coloradjusting windows in one pixel region, and respective windows areseparated from one another by lOpm or more in the pixel region. Also, aplurality of windows are arranged for respective pixel regions ofdifferent colors and arrangement directions of the plurality of windowsare different between the pixel regions of different colors in the colorfilter. Alternately, one window is arranged for respective pixel regionsof different colors and an arrangement direction of the window isdifferent between the pixel regions of different colors in the colorfilter. Also, pixel regions of different colors are directly adjacent toeach other not over a black mask in the color filter.

[0019] Also, a second aspect of the present invention is a liquidcrystal display device characterized by comprising a pair of firstsubstrate and a second substrate arranged facing to each other over aliquid crystal layer, the first substrate is formed pixels arranged inmatrix, and each pixel is formed a reflection portion to reflect anoutside light and a transmission portion to transmit a light, and thesecond substrate is formed a color filter for coloring respective pixelsto be different colors; wherein arrangement coordinates of thetransmission portion in a pixel is different between pixels colored tobe different colors.

[0020] According to the present invention, a reflection region and atransmission region form a common color filter in basically separatepixel region. Because different materials and separate productionprocesses are not applied for the reflection region and transmissionregion as in the conventional method, a cost reduction can be attained.On the reflection region, one or more color adjusting windows having acoloring concentration of zero or less than that of other portions isformed. By providing the windows, there is not much difference in colortone between the reflection region and the transmission region. In otherwords, a color filter applied to the transmission type is formed alloverthe pixel region and windows are provided on a part of the reflectionregion based on a specific rule. Due to this, it optically functions asa color filter applied to the reflection type. Consequently, a two-waytype color filter can be produced at a low cost without using specialmaterials for a color filter applied to a reflection type and withoutperforming a production process of a reflection type color filter.

BRIEF DESCRIPTION OF DRAWINGS

[0021]FIGS. 1A and 1B are schematic views of an example of aconventional hybrid type liquid crystal display device.

[0022]FIG. 2 is a plan view of a principle part of a liquid crystaldisplay device according to the present invention.

[0023]FIG. 3 is a flowchart of a production method of the liquid crystaldisplay device according to the present invention.

[0024]FIG. 4 is a schematic plan view of a conventional liquid crystaldisplay device.

[0025]FIG. 5 is a flowchart of a production method of a conventionalliquid crystal display device.

[0026]FIG. 6 is a graph of spectral transmittance of a conventionaltransmission CF.

[0027]FIG. 7 is a graph of spectral transmittance of a conventionalreflection CF.

[0028]FIG. 8 is a graph of spectral transmittance of a reflection CFaccording to the present invention.

[0029]FIG. 9 is a chromaticity diagram of the reflection CF according tothe present invention.

[0030]FIGS. 10A to 10C are disassembled perspective views of the generalconfiguration of a hybrid type liquid crystal display device.

[0031]FIGS. 11A to 11C are schematic views of a specific example of acolor filter according to the present invention.

[0032]FIGS. 12A and 12B are schematic views of a color filter accordingto a reference example.

[0033]FIG. 13 is a disassembled perspective view of the configuration ofa hybrid type liquid crystal display device according to the presentinvention.

[0034]FIG. 14 is a schematic view of a patterning method of a colorfilter.

[0035]FIGS. 15A and 15B are graphs of relative intensity distribution ofan exposure light amount.

[0036]FIG. 16 is a schematic plan view of a specific example of a colorfilter according to the present invention.

[0037]FIG. 17 is a chromaticity diagram of the color filter shown inFIG. 16.

[0038]FIG. 18 is a schematic plan view of another embodiment of a liquidcrystal display device according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0039] Below, preferred embodiments of the present invention will beexplained in detail with reference to the drawings.

[0040]FIG. 2 is a schematic plan view of a principle part of a liquidcrystal display device according to the present invention.

[0041] Generally, an active matrix type liquid crystal display devicecomprises a pair of a first substrate (CF substrate) and a secondsubstrate (TFT substrate) arranged facing to each other over a liquidcrystal layer. The TFT substrate is formed pixels PXL arranged inmatrix, and each pixel is formed a reflection portion for reflecting anoutside light and a transmission portion for transmitting a light. Onthe other hand, the CF substrate is formed a color filter colored to bedifferent colors corresponding to respective pixels PXL. In FIG. 2,pixels colored to be three primary colors, red, green and blue,respectively are shown as a set to facilitate understanding. This colorfilter CF comprises a reflection region CFR corresponding to thereflection portion and a transmission region CFT corresponding to thetransmission portion inside the pixel regions corresponding to therespective pixels PXL.

[0042] In the present embodiment, a common color filter is formed overboth of the reflection region CFR and the transmission region CFT.Accordingly, there is no difference between the reflecting color filterCF and the transmitting color filter CF in terms of materials. Instead,the reflection region CFR of the color filter CF is formed one or morecolor adjusting windows CFW having a coloring concentration of zero orless than that of other portions. Basically, by forming the windows(hereinafter, also referred to as CF windows) on the color filterapplied to the transmission type, optical characteristics required to acolor filter CF of the reflection region CFR are realized.

[0043] Namely, an equivalent reflecting CF can be formed by providingthe windows without using materials for a reflection CF.

[0044] Generally, the minimum unit that can be identified by human eyesis 30 μm square or so. By making the color adjusting CF windows as fineas 30 μm or less, an existence of the CF windows become visuallyindistinctive but able to adjust color tone of the color filter CF ofthe reflection region CFR.

[0045] Preferably, the color adjusting windows CFW are formed inside thereflection region CFR and away from the edges by 2 μm or more. Byarranging the windows CFW inside the pixel region, even when there is analignment error, the aperture ration of the windows is made constant bykeeping the windows not superposing with windows CFW of adjacent pixels.The aperture ration of the windows delicately affects color tone of thecolor filter, so that is has to be controlled at high accuracy. In thiscase, it is preferable to form the windows CFW inside the pixel regionby 2 μm or more considering an alignment error between pixels.

[0046] In the color filter according to the present embodiment, aplurality of color adjusting windows CFW are included in one pixelregion in some cases. In an example shown in FIG. 2, two CF windows arerespectively provided to red and green color filters. In this case, theCF windows are preferably formed away from each other by 10 μm or morein the pixel region. Generally, the CF windows can be formed by using aphotolithography technique. In this case, when considering resolution ofan exposure apparatus, etc., highly accurate CF windows can be formed byleaving a distance of 10 μm. When the CF windows get closer than that,it sometimes becomes difficult to separate the two in photolithography.

[0047]FIG. 3 is a flowchart of a production method of a CF substrateshown in FIG. 2.

[0048] First, a black mask for blocking a light is formed in a Blackprocess (ST1). Next, a transmission CF portion (CFT) and a reflection CFportion (CFR) of a pixel to be colored red among the RGB trio aresimultaneously exposed to form a red color filter (ST2). Then, in agreen pixel adjacent to the red pixel, the transmission CF portion andthe reflection CF portion are simultaneously exposed to form a greenfilter (ST3). Finally, in a blue pixel adjacent to the green pixel, thetransmission CF portion and the reflection CF portion are simultaneouslyexposed to form a blue color filter (ST4). In this case, at the time offorming color filters of the respective colors by exposure developmentprocessing, also CF windows can be opened at a time, so that therearises no burden in terms of processes.

[0049]FIG. 4 is an example of a conventional color filter. To facilitateunderstanding, the same reference numbers are used for portionscorresponding to the color filter of the present invention shown in FIG.2. In the conventional method, different color filter materials wereused for the transmission CF portion (CFT) and the reflection CF portion(CFR) in pixels of the respective colors. Generally, a material of theCFT has a higher coloring concentration than that of the CFR.

[0050]FIG. 5 is a flowchart of a production method of the color filtershown in FIG. 4. First, a black mask for blocking a light is formed in aBlack process (ST11). Next, a red color filter is formed only on atransmission CF portion as a part of a pixel (ST12). Then, a green colorfilter is formed on a transmission CF portion as a part of a green pixeladjacent to a red pixel (ST13). Next, a blue color filter is formed on atransmission CF portion as a part of a blue pixel adjacent to the greenpixel (ST14). After that, a red reflection CF is formed continuinglyfrom the transmission CF portion of the red pixel (ST15). Next, a greenreflection CF is formed continuingly from the transmission CF portion ofthe green pixel (ST16). Finally, a blue reflection CF is formedcontinuingly from the transmission CF portion of the blue pixel (ST17).From the above, RGB pixels comprising both of the transmission CFportion and the reflection CF portion are formed.

[0051] On the other hand, in the present invention, as shown in theflowchart in FIG. 2, the conventional coloring process can be halved.Note that the coloring order of red, green and blue can be changed inaccordance with characteristics of respective colors.

[0052]FIG. 6 illustrates a spectral transmittance of the transmissionportion CF of the blue pixel in the conventional method. In FIG. 6, theabscissa indicates a wavelength and the ordinate indicates atransmittance. The transmission portion CF of the blue pixel in theconventional method exhibits a peak of the transmittance at short of awavelength of 500 nm as shown in FIG. 6.

[0053]FIG. 7 illustrates a spectral transmittance of the reflectionportion CF of the blue pixel in the conventional method in the same way.In FIG. 7, the abscissa indicates a wavelength and the ordinateindicates a transmittance. Conventionally, different materials are usedin the transmission portion CF and the reflection portion CF, so thespectral transmittance are also different. The spectral transmittance ofthe reflection portion CF has a broader spectral characteristicscomparing with that of the transmission portion CF and the transmittancerises over the whole visible wavelength range.

[0054] On the other hand, in the present invention, the spectraltransmittance of the color filter is basically identical in thetransmission region and the reflection region. By opening the CF windowson the reflection region, a light transmitted through the CF windowreflects without being colored by the color of the color filter. Anobserver recognizes the most light reflected on the reflection portionof pixels and colored by the color filter together with a color-freelight as a part passed through the CF windows and, as a result,recognizes as a color, wherein a coloring concentration is faded, whichis similar to that of a conventional reflection type color filter.

[0055] Logically, the spectral transmittance in the case of furtherproviding the CF windows to the conventional transmission type CF can begiven from the following formula.

T _(CF) =T _(W) ² *S+T _(R) ²*(1−S)

[0056] Here, “T_(CF)” indicates a transmittance after combining, “T_(W)”indicates a transmittance of the CF windows, “S” indicates an apertureratio of the CF windows and “T_(R)” indicates a transmittance of the CF.Also, the aperture ratio “S” of the CF windows can be given from (anarea of CF window)/(a CF area of one pixel).

[0057]FIG. 8 illustrates spectral transmittance characteristics of acolor filter of the reflection region produced according to the presentinvention. Note that the spectral transmittance is obtained by asimulation based on the above formula and is a calculation result of thecase where a light transmits the color filter twice by assuming the caseof a reflection region. In FIG. 8, the abscissa indicates a wavelengthand the ordinate indicates transmittance.

[0058] Also, in FIG. 8, a curve “a” indicates a spectral transmittancewhen the aperture ratio of the CF windows is 15%. Similarly, a curve “b”indicates the case where the aperture ratio of the CF windows is 10%,and a curve “c” indicates the case where the aperture ratio of the CFwindows is 5%. Note that a curve “d” indicates a spectral transmittanceof a conventional transmission type CF. Here, the aperture ratio of theCF windows is important, and the total transmittance T_(CF) aftercombining can be adjusted by changing it.

[0059] To change the aperture ratio, a method of changing the number anda size of the CF windows can be applied. Namely, to optimize theaperture ratio, a color filter having spectral characteristics close tothose of a color filter applied to a conventional reflection type can beobtained. Also, the color tone widely changes when the aperture ratiochanges by a few percents or so, so that high processing accuracy isrequired for forming the CF windows.

[0060] Also, total chromaticity x and y of the color filter providedwith the CF windows can be obtained from the following formulas.$\begin{matrix}{X = {K*{\int_{380}^{780}{{T_{CF}(\lambda)}*{S(\lambda)}*{\overset{\_}{x}(\lambda)}\quad {\lambda}}}}} \\{Y = {K*{\int_{380}^{780}{{T_{CF}(\lambda)}*{S(\lambda)}*{\overset{\_}{y}(\lambda)}\quad {\lambda}}}}} \\{Z = {K*{\int_{380}^{780}{{T_{CF}(\lambda)}*{S(\lambda)}*{\overset{\_}{z}(\lambda)}\quad {\lambda}}}}} \\{K = \frac{100}{\int_{380}^{780}{{S(\lambda)}*{\overset{\_}{y}(\lambda)}\quad {\lambda}}}} \\{{x = \frac{X}{X + Y + Z}},{y = \frac{Y}{X + Y + Z}},{z = \frac{Z}{X + Y + Z}}}\end{matrix}$

[0061] Note that S(λ) indicates spectral intensity of a light source,{overscore (x)} (λ), {overscore (y)} (λ) and {overscore (z)} (λ) arecolor matching functions based on the CIE1931.

[0062] As is clear from the above formulas, chromaticity depends on theT_(CF). The xy chromaticity diagram in FIG. 9 is a graph thereof. Whenthe aperture ratio of the CF windows is increased from 5% to 15%, thechromaticity of the blue color filter moves to the center on the xyplane. By adjusting the aperture ratio of the CF windows, thechromaticity of the color filter can be optimally set.

[0063]FIGS. 10A to 10C are schematic views of the general configurationof a hybrid type liquid crystal display device.

[0064] In FIG. 10A to FIG. 10C, the reference number 10 indicates afirst (CF) substrate and 20 indicates a second (TFT) substrate. The TFTsubstrate 20 is formed signal lines 21, gate lines 22, pixel transistors23, reflection electrodes 24 and transparent electrodes 25.

[0065]FIG. 10A shows the general configuration of the first (CF)substrate 10. A red pattern, a green pattern and a blue pattern areformed in a stripe shape on a transparent base made by a glass, etc.Furthermore, a black pattern is formed to surround the RGB pattern. Asexplained above, the patterns of respective colors can be formed bysuccessively repeating film forming of photosensitive coloring materialand photolithography.

[0066]FIG. 10B shows three pixels of a liquid crystal display device. Aplurality of pixels are formed on the TFT substrate 20 side. Tocorresponding thereto, a red pattern, a green pattern, and a bluepattern in a stripe shape are formed on the CF substrate 10 side. Areflection electrode 24 composing a reflection portion and a transparentelectrode 25 composing the transmission portion are formed on respectivepixels on the TFT substrate 20. Furthermore, a pixel transistor 23 isformed to drive a pixel electrode composed of the reflection electrode24 and the transparent electrode 25. The pixel transistor 23 is a thinfilm transistor, wherein a gate electrode of the pixel transistor 23 isconnected to the gate line 22 and a source electrode is connected to thesignal line 21.

[0067]FIG. 10C is a further enlarged perspective view of one pixel. Acolor filter is formed on the CF substrate 10 so as to be correspondingto pixels formed on the TFT substrate 20. In the general configuration,the reflection region CFR corresponding to the reflection electrode 24and the transmission region CFT corresponding to the transparentelectrode use different color filter materials.

[0068] On the other hand, in the present invention, a common colorfilter is formed for the reflection region and the transmission region,and the CF windows are provided on the reflection region. A specificexample of the CF windows is shown in FIG. 11A to FIG. 11C. FIG. 11Ashows the configuration on the TFT substrate 20 side, wherein the pixelPXL is divided to a transmission portion T and the reflection portion R.A size of the pixel PXL is, for example, 100 μm×300 μm.

[0069]FIG. 11C is the configuration on the CF substrate 10 side producedaccording to the present invention, and one window CFW is formed in thereflection region. The CFW is formed inside the reflection region awayfrom the surrounding edges thereof by 2 μm or more. A size of the CFwindow is, for example, 60 μm×100 μm and the aperture ratio is set to20%.

[0070]FIG. 11B shows a reference example, wherein the window CFW isformed in the same way as in FIG. 11C but is not formed in thereflection region but extending to the surrounding edges of thereflection region.

[0071]FIGS. 12A and 12B illustrate a disadvantage of the case of forminga color filter of the reference example shown in 11B. The referencenumber WDT11 in FIG. 12A indicates a width of the CF window affected bydeviation, and the reference, number WDT12 in FIG. 12B indicates a widthof the original CF window.

[0072] As shown in FIG. 12A, when forming color filters, for example, inthe coloring order of R, G and B in the CF forming process, a greenpattern is aligned with respect to a red pattern by leaving a certainerror. Similarly, a blue pattern is aligned with respect to the greenpattern by leaving a certain error in the same way. As a result, asshown in FIG. 12A, there arises the case that the CF window is blockedby adjacent CFs due to the alignment errors. In this case, apredetermined aperture ratio of the CF windows cannot be maintained, andthere arises deviation of color tone on the color filter on thereflection region.

[0073] To prevent such a problem, as shown in FIG. 11C, it is sufficientif the CF window is formed away from edges of the CF by leaving adistance of at least an amount that the adjacent CFs are deviated due tothe alignment errors. Normally,. it is sufficient if the CF window isformed inside by leaving a distance of 2 μm or more from surroundingedges of the reflection region. More preferably, it is suitable to leave3 μm or more. Note that when alignment accuracy is improved, the limitof the distance naturally becomes less.

[0074]FIG. 13 is the overall configuration of a liquid crystal displaydevice wherein CF windows are formed on the reflection region of the CFsubstrate as explained above. The reference number D1O in FIG. 13indicates a distance between the transparent electrode 25 on the TFT 1side and a CF window.

[0075] As shown in FIG. 13, the CF substrate 10 is assembled to be aliquid crystal panel by being superposed with the TFT substrate 20. Thereflection electrode 24 on the TFT substrate 20 is formed by a lightreflecting film, and the transparent electrode 25 is formed by a lighttransmitting film. The both substrates 10 and 20 are superposed so thata pattern on the color filter on the CF substrate 10 superposes with apattern of the pixel electrode composed of the reflection electrode 24and the transparent electrode 25 on the TFT substrate 20. At this time,a CF window (CFW) is formed on the reflection region CFR on the CFsubstrate 10 side.

[0076] Accordingly, the CF window must not be superposed with thetransparent electrode portion on the TFT substrate 20 side. However,there actually arises an alignment error between the both substrates 10and 20 due to a mechanical error of a superposing apparatus. When suchalignment deviation arises, a CF window having a faded colorconcentration is observed through the transparent electrode, so that thedisplay quality is largely deteriorated. Thus, to prevent this, it ispreferable to form a CF window away from the transparent electrode 25 byleaving a distance caused by alignment deviation or more.

[0077] As a result, even if alignment deviation arises between the bothsubstrates, the transmission CF corresponds to the transparentelectrode, so that a color concentration does not deteriorate.Considering alignment accuracy between the both substrates, the distanceD10 between the CF window and edges of the transparent electrode 25 onthe TFT side is preferably 2 to 3 μm. Naturally, when alignment accuracyis improved, the limit of the distance can be made less.

[0078] Generally, an exposure apparatus for photolithography used in theCF process is called a proximity exposure apparatus, by which a parallellight is irradiated from the light source side to the mask. The exposureprocessing is performed in a state where mask and the substrate areclosely arranged by leaving certain constant distance so as not to toucheach other. The distance between the mask and the substrate at this timeis called an exposure gap and is a significant factor to determineexposure accuracy.

[0079]FIG. 14 is a schematic view of a patterning method of the colorfilter. In FIG. 14, the reference number 30 indicates a substrate, 31indicates a photomask, 32 indicates light block films and GP30 indicatesthe exposure gap.

[0080] As shown in FIG. 14, when the exposure gap GP30 is small,diffraction light intensity depending on a pattern arrangement of thelight block film 32 of the photomask 31 becomes small. When the exposuregap GP30 becomes large, the diffraction light intensity becomes largeand a diffraction pattern gradually increases. Therefore, patternforming faithful to the light block film 32 pattern on the photomask 31side becomes impossible.

[0081] Considering such a diffraction phenomena, when is arranging aplurality of CF windows adjacent to each other, it is important toarrange the CF windows having a certain distance in advance. Due tothis, a pattern unevenness caused by diffraction can be prevented. Inthe illustrated example, when the exposure gap GP30 is set to 150 μm, itis preferable that a distance between CF windows is 10 μm or more, morepreferably 20 μm or more. When reducing the exposure gap GP30, thedistance between the CF windows can be also reduced.

[0082] Note that, in the example shown in FIG. 14, a CF window is formedby forming a light block film 32 on the photomask 31 and performingexposure processing. In this case, since a coloring layer of the colorfilter is completely removed from the CF window, the coloringconcentration becomes 0. Instead of this, CF windows wherein the colorfilter on the CF window is left to a certain extent to have a loweredcolor concentration may be also used. Specifically, by creating a halfexposure condition by using a light block film pattern in a slit shape,a film thickness of the coloring layer of the CF window can be madethin.

[0083] Graphs in FIG. 15A and FIG. 15B show an exposure amount reachingto the substrate in the case where the exposure gap is set to 150um anda width size of the light block film pattern is set to 20 μm. FIG. 15Ashows the case where the distance between CF windows is set to 6.5 μm.On the other hand, FIG.15B shows the case where the distance between CFwindows is set to 15 μm. In FIG. 15A and FIG. 15B, the abscissaindicates a position on the substrate surface and the ordinate indicatesrelative intensity.

[0084] When the distance between the CF windows is 15 μm, a sufficientlight amount reaches between the CF windows and patterning faithful tothe light block film pattern becomes possible. On the other hand, whenthe distance between the CF windows is 6.5 μm, a sufficient exposurelight does not reach between the CF windows due to diffraction. Thismeans that size variation between the CF windows is easily caused.Furthermore, the exposure gap varies due to warps of the photomask orsubstrate surface. Even in such cases, a stable light amount can beobtained by separating adjacent CF windows by keeping a distance of atleast 10 μm, preferably 15 μm or more.

[0085]FIG. 16 is a schematic plan view of a specific example of the CFwindow of the color filter. FIG. 16 illustrates a set of RGB threepixels, wherein sizes of CF windows are optimized for the respective CFwindows to obtain preferable color tone for color display. In the bluepixel, one CF window is provided, by which the aperture ratio of 5% isaimed. In the red pixel, two CF windows are provided, by which theaperture ratio of 20% is aimed. Similarly, in the green pixel, two CFwindows are provided, by which the aperture ratio of 20% is aimed.

[0086] Not only by optimizing the number and size of the CF windows asabove, but by devising an arrangement thereof a so-called moire isprevented from arising. Namely, by setting different coordinates to bearranged of CF windows for respective pixels, a moire caused by a cyclicconfiguration is suppressed and the display quality is improved.Specifically, as shown in the figure, the CF windows are made not tohave the same distance and arrangement angles between respective RGBpixels.

[0087] When providing a plurality of CF windows, an arrangement of CFwindows of other color is made to have a different angle and distancefrom those of a CF window arrangement of the adjacent color. Due tothis, color unevenness due to the moire phenomenon can be prevented.

[0088] Namely, in a color filter according to the present invention,when arranging a plurality of windows respectively for pixel regions ofdifferent colors, arrangement directions of the plurality of windows aredifferent between pixel regions of different colors. Consequently, themoire can be prevented. Also, when arranging one window in therespective pixel regions of different colors, the arrangementcoordinates of the respective windows are different between pixelregions of different colors. Consequently, the moiré can be prevented.

[0089] In the specific example in FIG. 16, a black mask in lattice isnot formed between the RGB pixels, so that pixel regions of differentcolors are directly next to each other without the black mask. In thecase of such a configuration, declining of the contrast can be preventedby forming CF windows inside the respective pixel regions. Assuming thatthe windows are formed not inside the pixel regions but on the framesalong the pixel regions, the CF windows are formed exactly at theposition of the black mask. In such a pattern, a reflection light isemitted as it is from the lattice CF windows, so that the black levelbecomes weak and the contrast declines. On the other hand, since the CFwindows are provided inside the pixel regions in the present invention,the contrast can be maintained even in the configuration without a blackmask.

[0090]FIG. 17 is a graph of the chromaticity of a reflection CF of thecolor filter shown in FIG. 16. In the illustrated xy chromaticitydiagram, the CF chromaticity by the present invention is indicated by a“□” mark and the CF chromaticity by the conventional method is indicatedby a “Δ” mark. In the conventional method, a color filter adjusted to areflection region is used. On the other hand, in the present invention,a condition close to the chromaticity of the reflection CF is obtainedby providing CF windows to an originally transmission type color filter.As is clear from the graph, the chromaticity of the reflection CF by thepresent invention is almost the same as that of the reflection CF by theconventional method. As is clear from the FIG. 17, according to thepresent invention, it became possible to maintain complementary for thechromaticity while realizing a reduction of processes and reduction ofcosts.

[0091]FIG. 18 is a schematic view of other aspect of the presentinvention.

[0092] As explained above, a liquid crystal panel comprises a CFsubstrate 10 and a TFT substrate arranged facing to each other over aliquid crystal layer. As shown in the figure, the TFT substrate isformed pixels PXL arranged in matrix, and each pixel is formed areflection portion R to reflect an outside light and a transmissionportion T to transmit a light. On the other hand, the CF substrate isformed a color filter for coloring each of the pixels PXL to bedifferent colors (red, green and blue).

[0093] As is clear from FIG. 18, the arrangement coordinates of thetransmission portion T in a pixel differ between pixels PXL colored tobe different colors. By applying a random arrangement configuration asabove, a regular pattern is removed as much as possible and a moiré canbe suppressed.

Industrial Applicability

[0094] In a liquid crystal display device of the present invention, atransmission type color filter and a reflection type color filter aresimultaneously formed, so that the production process can be reduced to½ of the conventional method and a reduction of costs can be realized.Therefore, the liquid crystal display device can be applied, forexample, to a so-called hybrid type liquid crystal display devicewherein both of a reflection portion and a transmission portion areprovided in each pixel.

1. A liquid crystal display device, characterized by comprising a pairof first substrate and a second substrate arranged facing to each otherover a liquid crystal layer, said first substrate is formed pixelsarranged in matrix, and each pixel is formed a reflection portion toreflect an outside light and a transmission portion to transmit a light;and said second substrate is formed a color filter colored to bedifferent colors corresponding to respective pixels; wherein the devicecomprises one or more color adjusting windows having a coloringconcentration of zero or less than that of other portions are providedinside pixel regions corresponding to respective pixels and onreflection regions superposing with said reflection portions in saidcolor filter.
 2. A liquid crystal display device as set forth in claim1, characterized in that said color adjusting window is formed insidesaid reflection region leaving a distance of 2 μm or more from an edgeof the reflection region.
 3. A liquid crystal display device as setforth in claim 1, characterized in that said color filter comprises aplurality of color adjusting windows in one pixel region, and respectivewindows are separated from one another by 10 μm or more in the pixelregion.
 4. A liquid crystal display device as set forth in claim 1,characterized in that a plurality of windows are arranged for respectivepixel regions of different colors and arrangement directions of theplurality of windows are different between the pixel regions ofdifferent colors in said color filter.
 5. A liquid crystal displaydevice as set forth in claim 1, characterized in that one window isarranged for respective pixel regions of different colors and anarrangement direction of the window is different between the pixelregions of different colors in said color filter.
 6. A liquid crystaldisplay device as set forth in claim 1, characterized in that pixelregions of different colors are directly adjacent to each other not overa black mask in said color filter.
 7. A liquid crystal display device,characterized by comprising a pair of first substrate and a secondsubstrate arranged facing to each other over a liquid crystal layer,said first substrate is formed pixels arranged in matrix, and each pixelis formed a reflection portion to reflect an outside light and atransmission portion to transmit a light; and said second substrate isformed a color filter for coloring respective pixels to be differentcolors; wherein arrangement coordinates of said transmission portion ina pixel is different between pixels colored to be different colors.